The present invention generally relates to a dual magnet Hall effect switch. More particularly, the present invention relates to a push button, dual magnet Hall effect switch wherein the two magnets are aligned in parallel, in contact, and have opposite polarities.
The Hall effect occurs when charge carriers moving through a material experience a deflection because of an applied magnetic field. The deflection of the charge carriers results in a measurable electrical potential difference across the material. The potential difference is transverse to the magnetic field and the current direction. A Hall effect transducer measures the applied magnetic field and converts that measurement into a voltage. Hall effect transducers may be packaged to form commercially available Hall effect probes.
Many common applications may rely on the Hall effect and Hall effect probes. For instance, some computer keyboards employ a small magnet and a Hall effect probe to detect when a key is pressed. Some antilock brakes use Hall effect transducers to detect changes in a car wheel's rotational velocity, which can be used to calculate the appropriate braking pressure on each wheels. Additionally, Hall effect probes may be used to measure very small and slow fluctuations in a magnetic field, possibly down to one-hundredth of a gauss.
Hall effect probes may be used in a variety of applications and are particularly well-suited for use in contactless switches. A contactless switch typically includes a Hall effect probe, a magnetic field generator such as a magnet, and a mechanical activation means. In operation, a user activates the mechanical activation means, such as by flipping a switch. The mechanical activation means causes the magnet to move relative to the Hall effect probe. The movement of the magnet relative to the Hall effect probe induces a change in the magnetic field detected by the Hall effect probe. When the magnetic field reaches a predetermined level, the switch is treated as activated. Although the magnet is displaced relative to the Hall effect sensor, the magnet does not contact the sensor, nor does any electrical contact occur. Contactless switches offer improved reliability over conventional switches in which mechanical electrical contacts occur because contactless switches degrade less over time and are thus more reliable. For example, the mechanical contacts in a conventional switch may become corroded with use or alternatively the contacts may no longer form an acceptable electrical connection with use, Hall effect switches may be durable up to millions of actuations.
One useful example of a contactless Hall effect switch is U.S. Pat. No. 4,489,303 issued to Martin (hereinafter the Martin patent). The Martin patent discloses a contactless switch and joystick controller using Hall elements. FIGS. 4 and 5 of the Martin patent show contactless switches employing the Hall effect. Referring to FIG. 4, the contactless switch 60 includes a rod 74 having a magnet 86 mounted on one end, and a push button 80 mounted on the other end. A Hall effect switch 92 is positioned 20 below and in alignment with the rod 74. When the push button 80 on the rod 74 is depressed, the end of rod 74 upon which the magnet 86 is mounted is displaced towards the Hall effect switch 92. The displacement of the magnet 86 towards the Hall effect switch 92 generates a magnetic field at the Hall effect switch 92 which increases as the magnet 86 approaches. When the magnetic field detected at the Hall effect switch 92 reaches a predetermined level, the Hall effect switch 92 is actuated.
FIG. 5 of the Martin patent illustrates an alternate embodiment of a contactless switch 100 employing the Hall effect. The contactless switch includes a rod 74′ having a push button 80′ mounted on one end, a Hall effect switch 110 and two magnets 106, 108. The two magnets 106, 108 are mounted in the midportion of the rod 74′. Instead of the end-positioned Hall effect switch 60 of FIG. 4. the contactless switch 100 employs a Hall effect switch 110 mounted parallel to the axis of the rod 74′ near to the two magnets 106, 108. When the push button 80′ is engaged. the rod 74′ is displaced downward thus moving the two magnets 106, 108 with respect to the Hall effect switch 110. The movement of the two magnets 106, 108 relative to the Hall effect switch 110 produces a change in the magnetic field detected by the Hall effect switch 110. When the magnetic field detected at the Hall effect switch 110 reaches a predetermined level, the Hall effect switch 110 is actuated.
The two magnets 106, 108 of FIG. 5 are separated by a section of the rod 74′. The separation of the magnets may help to increase the region of linearity of the magnet's magnetic field. A large region of linearity is preferable in many applications because it allows the magnetic field to adjust more slowly with actuation, thus allows a detecting Hall Effect probe to track with greater accuracy.
The invention of the Martin patent is directed toward a video game. In switching applications outside of the video game arena, greater precision switches may be desired. That is, a more precise trigger point for the switch actuation is desired. Also, thermal effects may be encountered in some applications and may alter a switch's magnetic field or the sensitivity of the switch's Hall effect probe.
Thus, a need has long existed for a Hall effect switch having a greater switching precision and increased resistance to thermal effects.